html, body{
    margin: 0;
    padding: 0;

    ul{
        list-style: none;
        padding: 0;
        margin: 0;
        li{
            font-size: 13px;
            line-height: 30px;
            padding-left: 10px;
        }
    }
    .box{
        width: 500px;
        height: 230px;
        background: url('../images/开心.gif');
        background-size: cover;
    }
}